Locomotion Mechanism Research Articles

Synchrony and symmetry-breaking in active flagellar coordination.

Living creatures exhibit a remarkable diversity of locomotion mechanisms, evolving structures specialized for interacting with their environment. In the vast majority of cases, locomotor behaviours such as flying, crawling and running are orchestrated by nervous systems. Surprisingly, microorganisms can enact analogous movement gaits for swimming using multiple, fast-moving cellular protrusions called cilia and flagella. Here, I demonstrate intermittency, reversible rhythmogenesis and gait mechanosensitivity in algal flagella, to reveal the active nature of locomotor patterning. In addition to maintaining free-swimming gaits, I show that the algal flagellar apparatus functions as a central pattern generator that encodes the beating of each flagellum in a network in a distinguishable manner. The latter provides a novel symmetry-breaking mechanism for cell reorientation. These findings imply that the capacity to generate and coordinate complex locomotor patterns does not require neural circuitry but rather the minimal ingredients are present in simple unicellular organisms.This article is part of the Theo Murphy meeting issue ‘Unity and diversity of cilia in locomotion and transport’.

Analysis of Spiders' Joint Kinematics and Driving Modes under Different Ground Conditions.

Although the hydraulic transmission system in spider legs is well known, the spider's mechanism of locomotion during different terrain conditions still need to be explored further. In this study, spider locomotion was observed in detail on three pavement test platforms: horizontal hard pavement, horizontal soft pavement, and sloped soft pavement. The movement characteristics and joint kinematics of Grammostola rosea legs were captured by high-speed cameras and Simi Motion 3D tracking software. These observations showed that the gait pattern was basically consistent with an alternating tetrapod gait; however, the pattern observed on the sloped soft pavement was slightly different from that of the two horizontal pavements. In particular, the duty factor of the spiders was 0.683 when walking on the horizontal hard pavement, 0.668 on the horizontal soft pavement, and 0.630 on the sloped soft pavement. The duty factor was greater than 60% in all three pavement environments, which was minimal when walking on the sloped soft pavement. This pattern showed that spiders might have superior stability when walking, but their stability decreased in the sloped soft pavement environment. The ranges of joint angles through the spiders' gait cycles in every pavement environment were also analysed and compared. The findings showed that the hydraulically driven femur-patella and tibia-metatarsal joint angles varied widely, which confirmed that hydraulically driven joints had major functions and obvious effects on the walking process. The kinematic patterns identified in this study provide improved understanding of the hydraulic transmission mechanisms, the factors that affect motion stability, and the design of biomimetic systems.

Theoretical and numerical studies on a five-ray flexible pectoral fin during labriform swimming

Natural fish have evolved with an excellent swimming performance after millions of years. Based on the flexible features of the pectoral fin, this paper focuses on the kinematics and hydrodynamics of the fin when fish are swimming stably in still water in labriform mode. The locomotion mechanism based on the morphology of the pectoral fin is applied to establish a kinematic model composed of five rays and membranes, which is adopted to control the pectoral fin to reach deformation in approximately the same way as the labriform mode. A semi-empirical theoretical model based on the kinematics is proposed to calculate the hydrodynamic force. In order to study the flow field, the numerical simulation of fluid–structure interaction is carried out and the results are validated by the present semi-empirical model, which also verifies the feasibility of the semi-empirical theoretical model for describing the dynamics of the pectoral fin under a complex water environment. In addition, the relationship between propulsion performance and locomotion parameters (e.g. frequency of motion, amplitude of flapping and rowing angle, and phase lag between flapping and rowing) of the multi-degree of freedom flexible pectoral fin is also revealed. It is found that the frequency and amplitude of the flapping angle have a significant influence on the hydrodynamic thrust, while the rowing angle and phase lag have little effect. The established models and the results provide effective tools and significant reference for the design of bionic pectoral fins.

Design of a snake-like swimming mechanism based on wave propagation in a vibrating cantilever beam

In this study a locomotion mechanism which is similar to snake and fish swimming has been developed by using the natural vibration behavior of a simple cantilever beam (thin metal film). The swimming locomotion of the mechanism that is driven by wave propagation motion of the metal film has been confirmed by experiments. A metal cantilever beam (metal film), which is forced to vibrate at natural frequency by using a simple micro vibration motor, generates a propelling force, such as a fish fin that fluctuates in the liquid. And in this way, the swimming locomotion is provided in the specified directions depending on the orientation of the beam. In this way, it is aimed to develop an innovative and low energy consumption locomotion mechanism. The effects of design variables such as beam length and width, which effect the beam's natural frequency and locomotion performance, have been experimentally investigated on various test prototypes. The direction control and maneuverability of the robot can be improved by adding a second cantilever beam. Analytical calculations and experimental results showed the applicability of the proposed approach and the design. The locomotion mechanism introduced in the study has the potential to be used in micro robotic applications with its maneuverability and low energy consumption features.

A novel method for measuring asymmetry in kinematic and kinetic variables: The normalized symmetry index

Gait and movement asymmetries are important variables for assessing locomotor mechanics in humans and other animals and as a predictor of injury risk and success of clinical interventions. The four indices used most often to assess symmetry are not well designed for different variable types, perform poorly when presented with cases of high asymmetry or when variables are of low magnitude, and are easily influenced by small variation in the signal. The purpose of the present study was to test the performance of these indices on previously unpublished data on ACL-R patients and to propose a new index to resolve some of these limitations. The performance of four currently used indices and a new index—the Normalized Symmetry Index (NSI), which is scaled to the range of variables being tested across multiple trials—were compared using force and angular data on participants who had undergone anterior cruciate ligament reconstruction and healthy controls. The NSI performed well compared to all other indices with all variables and had the additional benefit of returning values that range from 0% (full symmetry) to ±100% (full asymmetry). Therefore, the NSI can serve as a universal index for assessing asymmetry in humans, nonhuman animal models, and in a clinical context for assessing risk for injury and clinical outcomes.

Grey Wolf Optimization-Based Second Order Sliding Mode Control for Inchworm Robot

SUMMARYThe flexible motion of the inchworm makes the locomotion mechanism as the prominent one than other limbless animals. Recently, the application of engineering greatly assists the inchworm locomotion to be applicable in the robotic mechanism. Due to the outstanding robustness, sliding mode control (SMC) has been validated as a robust control strategy for diverse types of systems. Even though the SMC techniques have made numerous achievements in several fields, some systems cannot be comfortably accepted as the general SMC approaches. Accordingly, this paper develops the Grey Wolf-Second order sliding mode control (GW-SoSMC) to control the manipulator of the inchworm robot. The GW-SoSMC reduces the chattering phenomenon of SMC and improves the controlling ability of SoSMC by weightage function. Subsequently, it compares the performance of the proposed method with several conventional techniques like Grey Wolf-SMC (GW-SMC), FireFly-SoSMC (FF-SoSMC), Artificial Bee Colony-SoSMC (ABC-SoSMC), Group Searching-SoSMC (GS-SoSMC), and Genetic Algorithm-SoSMC (GA-SoSMC). It portrays the valuable comparative analysis by measuring the accomplished joint angles, error, and response of the controller. Thus the proposed method discovers the supervisory controller for the inchworm robot that is immensely better than conventional controllers mentioned earlier.

An adhesive locomotion model for the rock-climbing fish, Beaufortia kweichowensis

The rock-climbing fish (Beaufortia kweichowensis) adheres to slippery, fouled surfaces and crawls both forward and backward in torrential streams. During locomotion, two suckers can be distinguished. Here, the general skeletal structure of the rock-climbing fish was determined using microtomography. Friction and adhesion were positively correlated, as were friction and fin ray angle. The unique adhesive locomotion system used by the rock-climbing fish was observed with a high speed camera. This system comprised two anisotropic suckers bearing two paired fins and two girdle muscles. A locomotion model was established based on these results. In this model, the fin states controlled the direction of motion using anisotropic friction, and alternate contractions of the girdle muscles provided propulsion during bidirectional crawling. This adhesive locomotion system was compared with other biological locomotion mechanisms. Based on these comparisons, we hypothesized that this novel system might represent an energy-saving solution for undulatory underwater vertical movement without detaching from the substrate.

Rodolfo Margaria and the First Walk on the Moon.

INTRODUCTION: During the Cold War years, the Space Race was largely supported by the efforts of many engineers and scientists, in particular human physiologists. Rodolfo Margaria (1901-1983), director of the Institute of Human Physiology at the University of Milan, was one of the most eminent and focused his studies on the mechanics of human locomotion in subgravity, in particular on the Moon's surface. Long before the real Moon landing, Margaria was able to correctly theorize how astronauts would walk on lunar soil, what would be the optimal pattern of progression, as well as determine the optimum and maximum speed at one-sixth of the Earth's gravity. On 21st July 1969 at 02:56 UTC, great excitement was aroused by the television images of Neil Armstrong's first steps on the Moon. Instead of walking, he moved around making small leaps, as expected from Margaria and colleagues.Grasso GS, Beretta EP, Miserocchi GA, Riva MA. Rodolfo Margaria and the first walk on the Moon. Aerosp Med Hum Perform. 2019; 90(11):982-985.

Friction reduction mechanism of the cuticle surface in the sandhopper talitrus saltator (Amphipoda, talitridae)

In many cases, strong friction reduction is critical for success of both living organisms and engineering systems. Some arthropods exhibit good antifriction abilities in their specific living environments and have inspired many innovations for solving industry challenges. However, the current literature mainly focused on terrestrial insects, such as beetles, grasshoppers and katydids. The antifriction mechanisms in amphibious arthropods are still unknown, even if their surfaces are optimized for both air and water environments. Herein the tribological properties of the cuticle surface of the sandhopper Talitrus saltator were studied using a universal microtribometer. Further investigations were developed to identify the microstructural, compositional, wettability, and mechanical properties of the sandhopper shell cuticles. It was found that increasing normal force can significantly reduce the coefficient of friction of the shell cuticle, especially for the alive and rewet sandhopper shells. The shell consists of bottle-like nano-caves in its exocuticle, nano-tubes in its mesocuticle, and gauze-like multilayers in its endocuticle. Under physiological conditions, glycoprotein-like fluid fillings exist in both the bottle-like caves and the nano-tubes below and cover on the shell surface. More importantly, a new antifriction mechanism of lubricant-squeezing nano-porous system was established for the sandhopper shell. This work can deepen our understanding in antifriction surfaces of amphibiotic crustaceans, and provide a potential approach to resolve the friction challenge in micro-machines, especially for the applications under aqueous condition. Statement of significanceFriction regulation is one of the critical mechanisms for animal locomotion in natural environments. However, not much is known about the mechanism of amphibious arthropods to reduce friction between their body and diverse environments, particularly achieving adaption under both air and aqueous conditions. We quantitatively study the microstructural, compositional and mechanical properties of the sandhopper (Talitrus saltator) shell cuticle and tribological behaviors under different conditions. Our results reveal the nano-porous system with fluid fillings for the sandhopper's shell and demonstrate the potential antifriction mechanism of this amphibious animal. We anticipate this work will inspire some effective antifriction designs for micro-machines, especially for their applications in complex environment like human body.

Ventral scale width in snakes depends on habitat but not hunting strategy

Abstract Environment and lifestyle induce substantial variation in the mechanisms of locomotion in vertebrates. A spectrum of adaptations related to locomotion is also present in limbless taxa, especially snakes, which have radiated successfully into a wide range of habitats. The majority of studies concerning habitat-driven variation in locomotor mechanisms of snakes have focused on the musculoskeletal system. Far less recognized is the variation in the morphology of ventral scales, which are another pivotal component of the locomotor system in snakes. Here, we investigated patterns of interspecific variation in the width of ventral scales in terms of lifestyle (hunting mode) and habitat occupied in 55 species of snakes belonging to eight families. We found that increasing terrestriality was associated with enlarged ventral scales. Reduction instead of maintenance of the width of ventral scales was observed in aquatic species, suggesting that wide ventral scales set constraints on aquatic locomotion. In terrestrial species, no significant differences were observed in terms of arboreality or hunting mode, which suggests overall optimization in the size of ventral scales towards terrestrial locomotion. Association between the width of ventral scales and locomotion can result in a habitat-dependent costs of abnormalities in ventral scale morphology, commonly observed in snakes.

Mechanisms of 3D cell migration.

Cell migration is essential for physiological processes as diverse as development, immune defence and wound healing. It is also a hallmark of cancer malignancy. Thousands of publications have elucidated detailed molecular and biophysical mechanisms of cultured cells migrating on flat, 2D substrates of glass and plastic. However, much less is known about how cells successfully navigate the complex 3D environments of living tissues. In these more complex, native environments, cells use multiple modes of migration, including mesenchymal, amoeboid, lobopodial and collective, and these are governed by the local extracellular microenvironment, specific modalities of Rho GTPase signalling and non-muscle myosin contractility. Migration through 3D environments is challenging because it requires the cell to squeeze through complex or dense extracellular structures. Doing so requires specific cellular adaptations to mechanical features of the extracellular matrix (ECM) or its remodelling. In addition, besides navigating through diverse ECM environments and overcoming extracellular barriers, cells often interact with neighbouring cells and tissues through physical and signalling interactions. Accordingly, cells need to call on an impressively wide diversity of mechanisms to meet these challenges. This Review examines how cells use both classical and novel mechanisms of locomotion as they traverse challenging 3D matrices and cellular environments. It focuses on principles rather than details of migratory mechanisms and draws comparisons between 1D, 2D and 3D migration.

Fluid-structure investigation of a squid-inspired swimmer

We propose a novel underwater propulsion system inspired by the jet-propelled locomotion mechanism of squids and other cephalopods. A two-dimensional nonaxisymmetric fluid-structural interaction model is developed to illustrate the physical mechanisms involved in the propulsive performance of this design. The model includes a deformable body with a pressure chamber undergoing periodic inflation and deflation motions enabled by attached springs and a nozzle through which the chamber is refilled and discharged (to form a jet). By using an immersed-boundary algorithm, we numerically investigate the dynamics of this system in the tethered mode. The thrust generation is found to increase with the frequency of body deformation, whereas the efficiency reaches a peak at a certain frequency. Examinations of the surrounding flow field illustrate a combination of vortices shed from the body and the nozzle. The optimal efficiency is reached when the nozzle-generated vortices start to dominate the wake. Our simulations also suggest that steady-state response can only be sustained for a few cycles before the wake is disturbed by a symmetry-breaking instability, which significantly affects the propulsive performance. Special strategies are needed to achieve stable long-distance swimming.

Medical Microrobot — A Drug Delivery Capsule Endoscope with Active Locomotion and Drug Release Mechanism: Proof of Concept

This paper presents a robotic capsule endoscope integrated a targeted drug delivery module (DDM) for digestive diseases treatments. The capsule with a big permanent magnet inside is wirelessly controlled and actively moves to target region in gastrointestinal tract by an electromagnetic actuation system (EMA). DDM is a separated body composed of a drug container and a non-power drug-releasing mechanism. The force to expel drug is generated by carbon dioxide gas pressure coming from a chemical reaction inside a propellant reservoir. Where the chemical reaction is activated by a mechanical mechanism that allows dry chemical powders contacting with water at the target point. A small permanent magnet is utilized to separate reagents and wet paper before drug injection. It is designed to be stable during locomotion by virtue of the attractive force of a big permanent magnet. To trigger releasing mechanism, gradient magnetic field from EMA system is created to push small magnet slide down, which allows reagents drop and contact with water in wet paper. The designed DDM has length of 11 mm and diameter of 11 mm. The proposed robotic capsule could show high potentials to be utilized for therapeutic treatment of digestive diseases in practical clinical sites through simulation and ex-vivo experiments.

Multi-stimuli-responsive programmable biomimetic actuator

Untethered small actuators have various applications in multiple fields. However, existing small-scale actuators are very limited in their intractability with their surroundings, respond to only a single type of stimulus and are unable to achieve programmable structural changes under different stimuli. Here, we present a multiresponsive patternable actuator that can respond to humidity, temperature and light, via programmable structural changes. This capability is uniquely achieved by a fast and facile method that was used to fabricate a smart actuator with precise patterning on a graphene oxide film by hydrogel microstamping. The programmable actuator can mimic the claw of a hawk to grab a block, crawl like an inchworm, and twine around and grab the rachis of a flower based on their geometry. Similar to the large- and small-scale robots that are used to study locomotion mechanics, these small-scale actuators can be employed to study movement and biological and living organisms.

An Adaptive Bioinspired Foot Mechanism Based on Tensegrity Structures.

Traditional robotic feet have received considerable attention for adaptive locomotion on complex terrain. As an alternative, tensegrity structures have the essential characteristics of deformability, adaptability to the environment, and impact resistance. This article proposes ways to solve the problem of adaptive locomotion on complex terrain based on a tensegrity structure and shows that this approach is particularly useful. On the basis of the locomotion mechanism and morphological structure of the human foot, a structural mapping model of a tetrahedral mast tensegrity structure is established through bionic mapping. A model of an adaptive foot mechanism is established through bioinspired design. Theoretical calculations of the behavior of the mechanism are derived, and the spring stiffnesses are matched. A theoretical method based on mechanical kinematics is presented, and a kinematic solution is realized through inverse kinematics. In addition, the locomotion of the mechanism, which is similar to that of the human foot, is simulated using ADAMS, and the effectiveness of the proposed theory and design method is verified by comparing the simulation output with the theoretically calculated results. Finally, a physical prototype manufactured using three-dimensional printing technology is used to experimentally verify the functional characteristics of the terrain-adaptive locomotion of the proposed mechanism. The results show that the proposed adaptive bioinspired foot mechanism exhibits good stability in an unstructured environment and can mimic the adaptive locomotion characteristics of the human foot on complex terrain remarkably well.

Mechanical characterization of the key portions in locust semi-lunar processes under different strain rates

The excellent rapid jumping and kicking of locusts are largely attributed to the power amplification mechanisms due to the semi-lunar processes (SLP) at their distal metathoracic femurs, especially dorsal-core (i.e., portion II) and ventral-core parts (i.e., portion III). The physiological range of strain rates at the two portions of locust SLP is quite broad in the periods of energy storage and release (approximately three orders). However, it still remains elusive how the mechanical properties of the two SLP portions change with the strain rate. We identified the elastic moduli and material compositions of SLP portions II and III by using nanoindentation and confocal laser scanning microscope. Apparent and creep-corrected reduced elastic moduli were calculated to represent the total energy absorption and storage, respectively. The results revealed that both portions II and III exhibit strain rate-sensitive elastic moduli, regardless of water content. The efficiency of elastic energy storage is only 51–70% in the case of low strain rate. This work can deepen our understanding in the energy storage and release mechanisms in locust locomotion and further provide guidelines for biomimetic design of power amplification apparatus in jumping robots.

Designing minimal and scalable insect-inspired multi-locomotion millirobots.

In ant colonies, collectivity enables division of labour and resources1-3 with great scalability. Beyond their intricate social behaviours, individuals of the genus Odontomachus4, also known as trap-jaw ants, have developed remarkable multi-locomotion mechanisms to 'escape-jump' upwards when threatened, using the sudden snapping of their mandibles5, and to negotiate obstacles by leaping forwards using their legs6. Emulating such diverse insect biomechanics and studying collective behaviours in a variety of environments may lead to the development of multi-locomotion robotic collectives deployable in situations such as emergency relief, exploration and monitoring7; however, reproducing these abilities in small-scale robotic systems with simple design and scalability remains a key challenge. Existing robotic collectives8-12 are confined to two-dimensional surfaces owing to limited locomotion, and individual multi-locomotion robots13-17 are difficult to scale up to large groups owing to the increased complexity, size and cost of hardware designs, which hinder mass production. Here we demonstrate an autonomous multi-locomotion insect-scale robot (millirobot) inspired by trap-jaw ants that addresses the design and scalability challenges of small-scale terrestrial robots. The robot's compact locomotion mechanism is constructed with minimal components and assembly steps, has tunable power requirements, and realizes five distinct gaits: vertical jumping for height, horizontal jumping for distance, somersault jumping to clear obstacles, walking on textured terrain and crawling on flat surfaces. The untethered, battery-powered millirobot can selectively switch gaits to traverse diverse terrain types, and groups of millirobots can operate collectively to manipulate objects and overcome obstacles. We constructed the ten-gram palm-sized prototype-the smallest and lightest self-contained multi-locomotion robot reported so far-by folding a quasi-two-dimensional metamaterial18 sandwich formed of easily integrated mechanical, material and electronic layers, which will enable assembly-free mass-manufacturing of robots with high task efficiency, flexibility and disposability.

Engineering passive swimmers by shaking liquids

The locomotion and design of microswimmers are topical issues of current fundamental and applied research. In addition to numerous living and artificial active microswimmers, a passive microswimmer was identified only recently: a soft, Λ-shaped, non-buoyant particle propagates in a shaken liquid of zero-mean velocity (Jo et al 2016 Phys. Rev. E 94 063116). We show that this novel passive locomotion mechanism works for realistic non-buoyant, asymmetric Janus microcapsules as well. According to our analytical approximation, this locomotion requires a symmetry breaking caused by different Stokes drags of soft particles during the two half periods of the oscillatory liquid motion. It is the intrinsic anisotropy of Janus capsules and Λ-shaped particles that break this symmetry for sinusoidal liquid motion. Further, we show that this passive locomotion mechanism also works for the wider class of symmetric soft particles, e.g. capsules, by breaking the symmetry via an appropriate liquid shaking. The swimming direction can be uniquely selected by a suitable choice of the liquid motion. Numerical studies, including lattice Boltzmann simulations, also show that this locomotion can outweigh gravity, i.e. non-buoyant particles may be either elevated in shaken liquids or concentrated at the bottom of a container. This novel propulsion mechanism is relevant to many applications, including the sorting of soft particles like healthy and malignant (cancer) cells, which serves medical purposes, or the use of non-buoyant soft particles as directed microswimmers.

Down Syndrome: Gait Pattern Alterations in Posture Space Kinematics.

Gait characteristics in Down syndrome (DS) are documented in terms of discrete kinematic variables. However, such features are strictly interrelated and reflect neurological and developmental delays. A phenotypical, quantitative assessment of how multi-joint walking patterns are activated and controlled during gait would enhance the understanding of locomotor mechanisms in such patients. We adopted an analysis framework based on principal component analysis: the gait kinematics of 221 patients aged 6-45 were expressed in terms of a reduced set of one-dimensional movement components. Their time course during the gait cycle was described by score vectors, here called principal positions; its second time derivative, called principal acceleration, characterized the activity of the neuromuscular controller on each component. Outcomes were compared to an age-matched group of 49 healthy individuals. After controlling for the effect of walking speed, we observed that the main alterations in gait patterns emerged in the fourth component which is mostly devoted to stability management (group differences, p < 0.001). Rather, the main sagittal-plane locomotor patterns showed only subtle differences from the control group. Using statistical parametrical mapping, we found when (step-to-step transitions) and how (interrelated joints motion) the fourth movement deviated from normal: in particular, an excessive hip adduction and trunk inclination during the transition between single and double support phases. These findings match the neurological and sensorimotor trait of DS and suggest the promotion of targeted rehabilitative interventions. Furthermore, this paper opens to the adoption of principal positions and principal accelerations to investigate the neuromuscular control of movement patterns during locomotion.

Four-wheel steering and driving mechanism for a reconfigurable floor cleaning robot

Abstract The fixed morphology cleaning robots lack adaptation to the unstructured environment to access and perform cleaning. Reconfigurable robots such as hTetro developed in our previous work have solved this problem, however the issues of robot's locomotion maneuverability and the associated real time control have not been resolved. This paper is aimed to validate whether a four wheel independently-controlled steering and driving (4WISD) mechanism can provide an effective solution for high maneuverability of the robot and can serve as a single mechanism for locomotion and transformation with a control strategy. After an extensive review of the existing reconfigurable robots including the hTetro platforms developed in our previous work and locomotion modules of mobile robots, the current hTetro platform with 4WISD mechanism is proposed. After it is designed and fabricated, experiments are conducted to verify its effectiveness. Experimental results show that the proposed 4WISD and the open loop kinematic control scheme deliver the high maneuverability of hTetro platform when following a circular path in various locomotion modes. The experimental results show the proposed 4WISD mechanism and kinematic controller make the hTetro platform achieve the desired maneuverability. In addition, the future work to improve the locking among the sub-modules of the robot and to further reduce the path deviation error of kinematic control is identified. Based on the work reported in this paper, the locking mechanism among the sub-modules of hTetro platform will be improved and the closed loop kinematic and dynamic control schemes will be developed to make it perform cleaning tasks in uncertain environments.